The disclosure relates generally to machine inspection, and more particularly, to a virtual turbomachine blade contact gap inspection.
In a turbomachine, blades are used to generate power from a flow of a working fluid. In particular, a number of blades may be coupled to a rotor to impart rotational motion to the rotor from a flow of a working fluid thereover. Turbomachine blades are initially shaped based on ideal models that create highly efficient blades. Each blade may include a shroud at an outer end thereof that includes a hard face that interacts with a mating hard surface of an adjacent blade's shroud. Hard faces are parts of the shroud that include wear material and come into contact with one another at a base load to dampen vibration. During turbine engine operation, shrouded turbine blades are subject to high amounts of distortion and twist. A contact gap between two adjacent blades is critical to ensure bucket engagement during turbomachine operation. As the turbomachine blades wear, the contact gap between two adjacent blades increases resulting in inadequate blade engagement. Consequently, turbomachine blade hard faces often require restoration during periodic repair processes.
After repair, an inspection is performed in order to ensure the blades have been properly restored. As part of the inspection, all of the blades of a particular stage are positioned in place on a rotor wheel by axially sliding the blades into place on mating couplings on the rotor wheel. The number of blades may vary depending on the blade stage, but is typically a relatively large number, e.g., 92, 100, etc. At this point, shims having a known size are placed between each adjacent pair of blade shrouds interacting hard faces. The cumulative dimension of the shims provides a measure of the cumulative dimension of all of the contact gaps between hard faces of the rotor wheel. A cumulative contact gap that is too large indicates unsuitability of the blades for continued use. In addition, an inability to place the shims into place between certain adjacent blade shrouds indicates that one or more blades may be too twisted for use, i.e., there is no contact gap between adjacent shroud hard faces. Further, a maximum allowable gap check may also be performed during the inspection. Once the inspection is complete, the blades are removed for shipment and installing at a turbomachine site. This inspection process poses a challenge in that the loading of the blades onto a rotor wheel, shimming all of the contact gaps, measuring the contact gaps/shims and removing all of blades is very labor intensive and time consuming.